What is the difference between Wait and Waitpid?

The wait and waitpid are system calls functions used in Unix/Linux operating systems to wait for child processes to finish. They have the following differences:

1. The difference lies in the parameters: the wait function does not require specifying the ID of the child process, whereas the waitpid function does.
2. Blocking behavior differs between the two functions: the wait function will block the calling process until any child process terminates, while the waitpid function allows for different options, such as choosing to return immediately without blocking the calling process.
3. There is a difference when handling multiple child processes: the wait function can only wait for any one child process to terminate, while the waitpid function can wait for a specified child process to terminate, or for any child process to terminate.
4. Error handling differs: the wait function does not allow for specifying the error handling method, whereas the waitpid function can specify to not block the calling process and immediately return 0 when there are no terminated child processes by setting the WNOHANG option.

In summary, the wait function is a relatively simple method to wait for a child process to terminate, while the waitpid function is more flexible, allowing the option to wait for a specific child process or return immediately without blocking the calling process.